The invention relates to an apparatus for treating particulate material, having a process chamber which is intended for receiving and treating the material and has a bottom which is composed of a plurality of overlapping guide plates which are placed one above the other and between which annular slots are formed, via which process air having an essentially horizontal component motion directed radially outward can be introduced.
Such an apparatus has been disclosed, for example, by DE 102 48 116 B3.
Such known apparatuses serve to dry, granulate or coat particulate material. A gaseous medium, “process air”, is introduced into the process chamber via the bottom and enters the process chamber in an approximately horizontally oriented manner through the numerous slots between the overlapping guide plates. Due to overlapping, annular guide plates, between which numerous slots are formed, a flow of process air directed radially from inside to outside forms in the process chamber and is deflected upward by the wall of the process chamber. The material to be treated is entrained in the process, but falls centrally downward on account of the gravitational force and again strikes the air cushion of the process air. If a certain extensive component is imposed on the process air, a toroidally revolving swirl flow ring gradually forms.
If larger agglomerates are to be formed from powders as fine as dust, that is to say if the material is to be granulated, a sticky medium is sprayed toward the toroidal ring via nozzles. In DE 102 48 116 B3 mentioned at the beginning, for example, spray nozzles directed obliquely upward are inserted into the wall of the container which encloses the process chamber.
During coating, a coating layer is to be applied as uniformly as possible to a larger body already present, that is to say said coating layer is to be sprayed on.
Various configurations of nozzles are known, the common feature of which is that a usually liquid or also particulate treatment substance is sprayed by means of spray air to form a fine mist. To this end, it has become known, for example, to expel the liquid under high pressure from a slot-shaped nozzle orifice and to spray it through spray-air orifices, whether on one side or on both sides of the liquid gap.
DE 102 32 863 A1 has disclosed an atomizing nozzle which has flow passages which are annular in cross section. Depending on the spray angle and looping angle, radiate, conical or more or less planar spray pancakes are produced. At a spray angle of 180° and a looping angle of 360° a virtually planar spray pancake is produced.
In this technology, which is widely used in the pharmaceutical field of application, it is attempted to achieve a result which is as uniform as possible, i.e. to achieve granulates with a very narrow grain size distribution, and to achieve during the coating a coating layer which is as uniform as possible, i.e. in particular a coating layer of identical thickness, at all particles of the charge which are contained in the apparatus. A considerable problem consists in the fact that material particles which wander around in an uncontrolled manner and are wetted with the moist and usually sticky spray liquid adhere to one another to form unwanted agglomerates.
Therefore precisely defined flow conditions which permit an optimum treatment result are desired in the toroidally rotating material band. In particular, it is desired that, after the spraying, the particles assume a flight path in which they move away from one another where possible and not toward one another in order to prevent undesirable agglomerates.
It is therefore the object of the present invention to provide for an improvement in such apparatuses for the treatment of particulate material to the effect that a harmonious sequence of movement with an optimum treatment result can be achieved.